As used herein the term gun barrel means any device having a projectile discharge bore wherein an exploding charge of propellant exerts a high gas pressure for a very short time on the projectile to eject it from the bore with desired ballistic characteristics. The present invention relates to gun barrels generally, without restriction as to bore size, and has particular utility with respect to gun barrels used in rapid fire weapons, because of the special problems which arise during use of such weapons. While the prior art discloses composite gun barrels, the applicant is not aware of any disclosure of the use of carbon fibers as structural elements in composite barrels.
The dynamic characteristics of gun barrels during use have received considerable attention in recent years in efforts to improve accuracy and reduce weight while maintaining the integrity of the barrels in terms of bore stiffness, erosion and strength. It is recognized, for example, that accuracy is adversely affected by vibrations which are induced by the stresses which are transmitted to the barrel as a result of the movement of the projectile through the bore. The vibrations can produce a significant transverse force component on the projectile at the instant of its departure from the bore as well as physical displacement and misalignment. As a a result there is likely to be a shift in the flight path of each successive projectile from a rapid fire weapon. Further, it is recognized that with a rifled bore the forces of acceleration coupled with the resistance of the projectile against the driving side of the lands of the rifling create a torque which may cause an angular displacement of perhaps 2.degree. in the barrel. This torque is not detrimental in single shot fire because the barrel elastically returns to its original geometry before the next shot. However, in the case of rapid fire guns (e.g. a firing rate such as 800 rounds per minute) the torque induced by projectile rotational acceleration causes torsional vibration which is still active at the time the next projectile is fired. This results in a dynamic condition such that the geometry of the barrel may be different for each projectile. Thus, with rapid fire guns there is a dispersion of the cone of fire which is much greater than for static fire guns. It is estimated, for example, that the cone of fire for a 50 caliber machine gun at a range of 300 yards is ten feet.
Composite gun barrels are described in the prior art. U.S. Pat. No. 2,847,786 describes a composite barrel having a metal liner forming the bore and an exterior jacket of wound glass fibers or fibers of synthetic polymeric material bonded together with a binder such as a synthetic resin. U.S. Pat. No. 3,228,298 also describes gun barrels constructed of a metal liner and a jacket of glass fiber reinforced plastic. Neither of these patents describes the use of carbon filaments in the jacket.
U.S. Pat. No. 4,341,823 describes metal-coated carbon filaments such as nickel coated filaments. The coating may be applied by a vapor deposition technique, electroplating or by an electroless technique. The patent also describes carbon-filament reinforced metal matrix composite bodies formed by immersing bundles of metal coated carbon fibers in molten metal or by placing a bundle of such fibers in a mold cavity and applying molten metal. The patent does not disclose a gun barrel having a carbon fiber/metal matrix jacket on a bore-forming liner.
U.S. Pat. No. 4,223,075 describes carbon-filament-reinforced metal matrix composites, such as structural components in the form of rods and plates, made by first forming wire-like metal-carbon filaments, placing parallel bundles of the wire-like composites in molds, and consolidating the composites into an integral mass by heating and compacting. No mention of gun barrels is made.
Other U.S. patents which disclose metal coated carbon fibers, without reference to their possible use for manufacturing gun barrels, are U.S. Pat. Nos. 3,720,257 and 3,821,024.
U.S. Pat. No. 3,641,870 describes a completely non-metallic gun barrel, especially a mortar tube, made of glass fiber reinforced synthetic resin.